<?php
/**
 * 短地址
 * 
 * @copyright  Copyright (c) 2012 www.Mediad.cn
 * @license    New BSD License
*/
class Mediad2_Utility_Shorturl
{
	/**
	 * Translates a number to a short alhanumeric version
	 *
	 * Translated any number up to 9007199254740992
	 * to a shorter version in letters e.g.:
	 * 9007199254740989 --> PpQXn7COf
	 *
	 * specifiying the second argument true, it will
	 * translate back e.g.:
	 * PpQXn7COf --> 9007199254740989
	 *
	 * this function is based on any2dec && dec2any by
	 * fragmer[at]mail[dot]ru
	 * see: http://nl3.php.net/manual/en/function.base-convert.php#52450
	 *
	 * If you want the alphaID to be at least 3 letter long, use the
	 * $pad_up = 3 argument
	 *
	 * In most cases this is better than totally random ID generators
	 * because this can easily avoid duplicate ID's.
	 * For example if you correlate the alpha ID to an auto incrementing ID
	 * in your database, you're done.
	 *
	 * The reverse is done because it makes it slightly more cryptic,
	 * but it also makes it easier to spread lots of IDs in different
	 * directories on your filesystem. Example:
	 * $part1 = substr($alpha_id,0,1);
	 * $part2 = substr($alpha_id,1,1);
	 * $part3 = substr($alpha_id,2,strlen($alpha_id));
	 * $destindir = "/".$part1."/".$part2."/".$part3;
	 * // by reversing, directories are more evenly spread out. The
	 * // first 26 directories already occupy 26 main levels
	 *
	 * more info on limitation:
	 * - http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/165372
	 *
	 * if you really need this for bigger numbers you probably have to look
	 * at things like: http://theserverpages.com/php/manual/en/ref.bc.php
	 * or: http://theserverpages.com/php/manual/en/ref.gmp.php
	 * but I haven't really dugg into this. If you have more info on those
	 * matters feel free to leave a comment.
	 *
	 * The following code block can be utilized by PEAR's Testing_DocTest
	 * <code>
	 * // Input //
	 * $number_in = 2188847690240;
	 * $alpha_in  = "SpQXn7Cb";
	 *
	 * // Execute //
	 * $alpha_out  = alphaID($number_in, false, 8);
	 * $number_out = alphaID($alpha_in, true, 8);
	 *
	 * if ($number_in != $number_out) {
	 *	 echo "Conversion failure, ".$alpha_in." returns ".$number_out." instead of the ";
	 *	 echo "desired: ".$number_in."\n";
	 * }
	 * if ($alpha_in != $alpha_out) {
	 *	 echo "Conversion failure, ".$number_in." returns ".$alpha_out." instead of the ";
	 *	 echo "desired: ".$alpha_in."\n";
	 * }
	 *
	 * // Show //
	 * echo $number_out." => ".$alpha_out."\n";
	 * echo $alpha_in." => ".$number_out."\n";
	 * echo alphaID(238328, false)." => ".alphaID(alphaID(238328, false), true)."\n";
	 *
	 * // expects:
	 * // 2188847690240 => SpQXn7Cb
	 * // SpQXn7Cb => 2188847690240
	 * // aaab => 238328
	 *
	 * </code>
	 *
	 * @author	Kevin van Zonneveld <kevin@vanzonneveld.net>
	 * @author	Simon Franz
	 * @author	Deadfish
	 * @copyright 2008 Kevin van Zonneveld (http://kevin.vanzonneveld.net)
	 * @license   http://www.opensource.org/licenses/bsd-license.php New BSD Licence
	 * @version   SVN: Release: $Id: alphaID.inc.php 344 2009-06-10 17:43:59Z kevin $
	 * @link	  http://kevin.vanzonneveld.net/
	 *
	 * @param mixed   $in	  String or long input to translate
	 * @param boolean $to_num  Reverses translation when true
	 * @param mixed   $pad_up  Number or boolean padds the result up to a specified length
	 * @param string  $passKey Supplying a password makes it harder to calculate the original ID
	 *
	 * @return mixed string or long
	 */
	public function alphaID($in, $to_num = false, $pad_up = false, $passKey = null)
	{
		$index = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
		if ($passKey !== null) {
			// Although this function's purpose is to just make the
			// ID short - and not so much secure,
			// with this patch by Simon Franz (http://blog.snaky.org/)
			// you can optionally supply a password to make it harder
			// to calculate the corresponding numeric ID
	
			for ($n = 0; $n<strlen($index); $n++) $i[] = substr( $index,$n ,1);
	
			$passhash = hash('sha256',$passKey);
			$passhash = (strlen($passhash) < strlen($index))
				? hash('sha512',$passKey)
				: $passhash;
	
			for ($n=0; $n < strlen($index); $n++) $p[] =  substr($passhash, $n ,1);
	
			array_multisort($p,  SORT_DESC, $i);
			$index = implode($i);
		}
	
		$base  = strlen($index);
	
		if ($to_num) {
			// Digital number  <<--  alphabet letter code
			$in  = strrev($in);
			$out = 0;
			$len = strlen($in) - 1;
			for ($t = 0; $t <= $len; $t++) {
				$bcpow = bcpow($base, $len - $t);
				$out   = $out + strpos($index, substr($in, $t, 1)) * $bcpow;
			}
	
			if (is_numeric($pad_up)) {
				$pad_up--;
				if ($pad_up > 0) $out -= pow($base, $pad_up);
			}
			$out = sprintf('%F', $out);
			$out = substr($out, 0, strpos($out, '.'));
		} 
		else 
		{
			// Digital number  -->>  alphabet letter code
			if (is_numeric($pad_up)) {
				$pad_up--;
				if ($pad_up > 0) $in += pow($base, $pad_up);
			}
	
			$out = "";
			for ($t = floor(log($in, $base)); $t >= 0; $t--) {
				$bcp = bcpow($base, $t);
				$a   = floor($in / $bcp) % $base;
				$out = $out . substr($index, $a, 1);
				$in  = $in - ($a * $bcp);
			}
			$out = strrev($out); // reverse
		}
	
		return $out;
	}

	/**
	 * 获得密码，默认passkey=password
	 * 
	 * @param mixed $in
	 * @param boolean $to_num
	 * @param int $pad_up
	 */
	public function getPass($in, $to_num = false, $pad_up = false)
	{
		$passKey = 'password';
		return $this->alphaID($in, $to_num, $pad_up, $passKey);
	}
	
	/**
	 * 获得短地址，默认passkey=Null
	 *
	 * @param mixed $in
	 * @param boolean $to_num
	 * @param int $pad_up
	 * @param string $passKey
	 */
	public function getShorturl($in, $to_num = false, $pad_up = false, $passKey = null)
	{
		return $this->alphaID($in, $to_num, $pad_up, $passKey);
	}

}

